(a) The Commissioner of Revenue Services may examine the records of any hospital subject to a tax imposed under the provisions of sections 12-263a to 12-263e, inclusive, as he may deem necessary. If he shall determine therefrom that there is a deficiency with respect to the payment of any such tax due under the provisions of said sections 12-263a to 12-263e, inclusive, he shall assess the deficiency in tax, give notice of such deficiency assessment to the hospital and make demand thereupon for payment. Such amount shall bear interest at the rate of one per cent per month or fraction thereof from the date when the original tax was due and payable. When it appears that any part of the deficiency for which a deficiency assessment is made is due to negligence or intentional disregard of the provisions of said sections 12-263a to 12-263e, inclusive, or regulations adopted thereunder, there shall be imposed a penalty equal to ten per cent of the amount of such deficiency assessment, or fifty dollars, whichever is greater. When it appears that any part of the deficiency for which a deficiency assessment is made is due to fraud or intent to evade the provisions of sections 12-263a to 12-263e, inclusive, or regulations adopted thereunder, there shall be imposed a penalty equal to twenty-five per cent of the amount of such deficiency assessment. No hospital shall be subject to more than one penalty under this subsection in relation to the same tax period. Within thirty days of the mailing of such notice, the hospital shall pay to the commissioner, in cash, or by check, draft or money order drawn to the order of the Commissioner of Revenue Services, any additional amount of tax, penalty and interest shown to be due.

(b) Except in the case of a wilfully false or fraudulent return with intent to evade the tax, no assessment of additional tax shall be made after the expiration of more than three years from the date of the filing of a return or from the original due date of a return, whichever is later. If no return has been filed as provided under the provisions of § 12-263b, the commissioner may make such return at any time thereafter, according to the best information obtainable and according to the form prescribed. Where, before the expiration of the period prescribed herein for the assessment of an additional tax, a hospital has consented in writing that such period may be extended, the amount of such additional tax due may be determined at any time within such extended period. The period so extended may be further extended by subsequent consents in writing before the expiration of the extended period.

(c) The commissioner may enter into an agreement with the Commissioner of Social Services delegating to the Commissioner of Social Services the authority to examine the records and returns of any hospital subject to the tax imposed under § 12-263b and to determine whether such tax has been underpaid or overpaid. If such authority is so delegated, examinations of such records and returns by the Commissioner of Social Services and determinations by the Commissioner of Social Services that such tax has been underpaid or overpaid shall have the same effect as similar examinations or determinations made by the Commissioner of Revenue Services.